John Gill Commentary Genesis 25:12

"Now these are the generations of Ishmael, Abraham`s son, whom Hagar the Egyptian, Sarah`s handmaid, bare unto Abraham." — Genesis 25:12 (ASV)

Now these [are] the generations of Ishmael, Abraham's son, &c.] Or the genealogy of his posterity; and which is given to show that the Lord was not unmindful of his promise made to Abraham, concerning the multiplication of his seed, (Genesis 16:10) (17:20): whom Hagar the Egyptian, Sarah's handmaid, bore unto Abraham; see (Genesis 16:1Genesis 16:15).